1. Field of the Invention
The invention relates to a threaded connector, and more particularly to a gas-sealing threaded connector.
2. Description of the Related Art
Nowadays, threaded connectors are widely used in exploiting underground natural gas, and high gas-sealing performance thereof must be ensured.
FIG. 1 illustrates a conventional threaded connector, in which a conical or spherical sealing surface is formed on a small end of external thread of a pipe, and another conical or spherical sealing surface is formed on a small end of internal thread of a coupling fit therewith. As the external thread is tightly fit with the internal thread, appropriate interference is generated between the sealing surfaces thereby facilitating sealing of gas.
Normally, threads of a tubing and casing operate for connection. After the external thread is tightly fit with the internal thread, a gap exists in a part of a thread tooth, and thus one or two spiral leakage channels A and B are formed, which leads to leakage of high pressure gas, as shown in FIGS. 2 and 3.